In the automobile field, developments in automation have enabled to equip vehicles with a starting device by radio-identification. Such a device comprises an active transponder periodically emitting an electromagnetic field to remotely communicate with a corresponding radio reader in the vehicle. For reasons of ease and space requirement, the starting device comprises a housing containing the transponder, a micro-antenna, and a power source. The presence of this power source, generally in the form of a battery, has several disadvantages, particularly related to the discharge and the oxidation of the battery in case of non-sealed boxes.
Furthermore, document KR101255928 proposes a ring-shaped battery-free radio device making it possible to do without a device of the key or housing type. However, this device tends to inadvertently trigger or unlock the associated system without control of the wearer. Indeed, a passive NFC or RFID chip is capable of emitting when an antenna emits electromagnetic waves within range, thereby constituting a lack of security.